1. Field of the Invention
The present invention relates generally to electrical wiring devices, and particularly to electrical wiring devices that include electric circuit protective features.
2. Technical Background
The average consumer is so used to having electric power at his beckon call, that he often forgets, or does not know, how that electric power is delivered to him. The terms “electrical wiring device” or “electrical circuit” are thus very often abstractions to the typical consumer. As such, it may be useful to provide a brief review of the terminology that is used to describe the technologies related to the delivery of electric power within a structure or a residence.
AC electric power service provided by the power utility is usually terminated by a breaker panel located within the residence. Very often the breaker panel is disposed in the basement of the structure if it has one. The breaker panel distributes the electric power to various branch circuits throughout the structure such that each branch circuit is monitored and controlled by a circuit breaker. If the circuit breaker detects a fault condition it will trip the breaker to interrupt the delivery of power to that circuit. Moreover, the consumer may manually actuate the breaker switch to interrupt the delivery of power to that circuit. The breaker switches may be rated at 20 A or 15 A depending on the nature of the branch circuit.
The backbone of a single phase branch circuit typically includes a cable that has a black (hot) wire, a white (neutral) wire and a green (ground) wire. In some cases, only two wires (hot and neutral) are employed. An additional hot wire is required for each additional phase such that a two phase circuit may include four wires and a three phase circuit may include five wires. The conventional method for installing electrical circuits includes a “rough-in” installation phase and a finish installation phase. In the rough-in phase, conduit or cable is disposed throughout the structure in accordance with the building plans. Junction boxes are installed at appropriate locations to house electrical connection points where two or more conductors can be spliced together. Device boxes are installed throughout the structure where electrical service is desired. After the boxes are placed, the electrical wires are pulled through the conduits (if provided) and all of the circuits are bonded such that the neutral conductors are connected to ground at or near the circuit breaker.
The electrical wiring in a branch electric circuit typically interconnects one or more electrical wiring devices. One or more electrical wiring devices may be mounted to a device box depending on the size of the device box. A single-gang device box typically accommodates one electrical wiring device; a two-gang device box will typically accommodate two electrical wiring devices, and so on and so forth. An electrical wiring device provides the consumer with a point of access to electrical service. For example, a receptacle outlet provides power to a portable device when the device's corded power plug is inserted into an energized receptacle. Once an electrical wiring device is installed inside the device box, a cover plate is disposed over the electrical wiring device to “complete the electrical enclosure” such that individuals are not exposed to “hot” electrical wiring after the electrical power is turned ON.
From a structural standpoint, an electrical wiring device is disposed within an electrically non-conductive housing, and nowadays that non-conductive material is usually made from a hard plastic material. A set of line terminals, a set of load terminals and often a ground connection are provided at the exterior of the electrical wiring device and are connected to electrical components or conductors disposed in the interior of the device. The “line terminals” of an electrical wiring device refers to the terminals that connect the wiring device to conductive wires from the breaker panel. The “load terminals” or the “feed-through load terminals” are connected to downstream wiring that is configured to propagate AC power to one or more downstream electrical loads. The term “receptacle load terminals” refers to a receptacle outlet that provides power to a portable load when a corded power plug is inserted therein. A load, of course, refers to an appliance, a lighting device, or some other kind of device that consumes electrical power during operation.
Certain types of electrical faults are known to occur in branch electric circuits and electrical wiring systems. These faults represent serious safety issues that may result in fire, shock or electrocution if not addressed properly. Electric circuit protection devices are deployed in the branch electric circuits to prevent the consumer from being shocked or electrocuted when such faults occur. These protective devices usually include a circuit interrupter disposed between the line terminals and the load terminals. The circuit interrupter provides power to the load terminals under normal conditions; however, when the protective device detects a fault condition in the load circuit, it will trip the circuit breaker to interrupt electrical connectivity between the line terminals and the load terminals. There are many types of electric circuit protection devices including ground fault circuit interrupters (GFCIs), arc fault circuit interrupters (AFCIs), transient voltage surge suppressors (TVSSs), or surge protective devices (SPDs). This list includes representative examples and is not meant to be exhaustive and a single device may be configured to perform one or more of these functions (e.g., a combination AFCI/GFCI).
There are several drawbacks associated with conventional installation methods and conventional protective electrical wiring devices. Conventional protective electrical wiring devices often do not make efficient use of space. In addition, mounting the wiring device's ground strap to the device box is tedious, time consuming, and therefore costly. The same can be said of mounting the cover plate to the electrical wiring device. Moreover, in multi-gang installations, the finished look is often ragged because the plurality of electrical devices and their respective cover plates are typically not in alignment. This misalignment can be, and very often is, in all three dimensions. Retrofitting an electrical installation can also be problematic from the standpoint of the finished look because the device box, or an old work box, may not be precisely aligned to the plane of the wall surface. This is especially true if the wall surface itself is uneven. After remodeling a space, homeowners often seek to replace an existing wall plate with one that better matches the new décor. Thus, a homeowner may inadvisably remove the faceplate cover from an energized wiring device and inadvertently become exposed to a shock hazard from the “hot” electrical wiring.
What is needed therefore is a protective electrical wiring device system that addresses the drawbacks articulated above. In particular, what is needed is a protective electrical wiring device that may be employed in a number of different form factors without having to modify the internal electro-mechanical configuration of the device. Stated differently, a protective device is needed that can be configured in a conventional form factor or in another form factor suitable for use in a modular framing system such that it does not require fasteners to be securely installed within the device box.